Machine for inspecting glass containers

ABSTRACT

A machine for distinguishing blisters from checks on the finish of a glass container. The center of each captured object in an array is determined by a controller which determines the object centers in a plurality of adjacent bands. The band having the most object centers is determined and the objects in the band having the most object centers are deleted from the rest of the bands. The control repeatedly determines the band of the rest of the bands having the most object centers and deletes the objects in the band of the rest of the bands having the most object centers from the remainder of the bands until the objects in each band are unique. The maximum separation of objects in each band is defined and checks will be differentiated from blisters based on this separation.

The present invention relates to machines, which inspect glasscontainers for defects, and more particularly, to a system whichinspects for checks (cracks) in translucent glass containers.

BACKGROUND OF THE INVENTION

In the glass container industry, small cracks, or fracture in the glassare referred to as “check defects”. Checks can range from submillimeters to several hundred millimeters and can be oriented at anydirection from vertical to horizontal. Glass is not a crystallinestructure by nature, but most cracks propagate roughly along a plane ofsome orientation in space mostly determined by the shape of the glass atthat location. Most of these crack defects will drastically weaken thebottle, often causing it to rupture or to leak. Therefore, it is verylikely that a bottle manufacturer will remove a container with a checkbefore it reaches filling plants. Checks appearing near the mouth of thecontainers are called finish checks. In the glass bottle industry, theterm “container finish” refers to the portion of the bottle that definesthe mouth, threads or beads, and the ring. The upper surface of themouth is referred to as the sealing surface.

Another anomaly, which can also be present are bubbles. A bubble resultswhen gas is trapped in the glass. When the bubbles are large they arereferred to as a blister and when the bubbles are small, they arereferred to as a seed. The presence of bubbles, while affecting theappearance of the bottle, do not necessarily require the rejection ofthe bottle and an operator may allow such a bottle to be packed. Forpurposes of this application, the word blister will include a seed.

The following U.S. Pat. Nos. 4,701,612, 4,945,228, 4,958,223, 5,020,908,5,200,801, 5,895,911, 6,104,482, 6,211,952, and 6,275,287 all relate todevices that detect defects in the finish of a container.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an apparatus forinspecting glass containers, which can differentiate vertical,horizontal, and any other angle cracks (checks) from blisters.

Other objects and advantages of the present portion of this inventionwill become apparent from the following accompanying drawings, whichillustrate, in accordance with the mandate of the patent statutes, apresently preferred embodiment incorporating the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become apparent from the following accompanyingdrawings which illustrate, in accordance with the mandate of the patentstatutes, a presently preferred embodiment.

FIG. 1 is an oblique elevational schematic view of a prior artinspection station of a machine for inspecting glass containers forchecks and other defects;

FIG. 2 is a schematic top view of the container at the prior artinspection station showing the light axes of a pair of light sources andthe camera;

FIG. 3 is a schematic elevational view showing the light axes of theprior art light sources and camera shown in FIG. 2;

FIG. 4 is a control drawing showing how an unwrapped image is defined;

FIG. 5 is a view, taken from the camera, of the finish area of thebottle shown in FIG. 1, illustrating images captured each θ (theta)degrees of rotation of the bottle about its vertical axis through anangle φ (phi);

FIG. 6 is a schematic illustration of the unwrapping process illustratedin FIG. 4;

FIG. 7 is a presentation of 10 images of an object captured through 11locations spaced θ (theta) degrees apart through an angle of φ (phi)degrees with the center of the object plotted;

FIG. 8 is presentation similar to that of FIG. 8 showing only theobjects in band 1-2;

FIG. 9 is presentation similar to that of FIG. 8 showing only theobjects in band 2-3;

FIG. 10 is presentation similar to that of FIG. 8 showing only theobjects in band 3-4;

FIG. 11 is a control drawing showing the structure of the control fordetermining whether a captured object is a check or a blister; and

FIG. 12 is a control drawing illustrating the structure for identifyinga bottle for rejection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a machine for inspecting glass containers (bottles), the containers10 are transported vertically along a conveyor 12 to an inspectionstation illustrated in FIG. 1. The conveyor may be a linear belt or aturret type feed system. A container 10 is engaged by upper and lowerrear pairs of idler rollers 14 and a front drive wheel 16 so thatrotation of the drive wheel in the clockwise direction will rotate thecontainer in the counterclockwise direction. There is conveyor dwell ofsufficient duration at the inspection station so that the container canbe rotated more than 360 degrees while inspection takes place. Acontainer present sensor 18 will sense the presence of a container atthe inspection station. Conical light sources (Light Source #1/20 andLight Source #2/21) which can be configured from L.E.D.'s, illuminatethe finish portion of the container and a Camera/22 images the finishportion. As can be seen from FIGS. 2 and 3, the Light Axis for eachlight source, which is in the positive “Z” plane of the container, ishorizontal, and intersects the axis “A” of the container. The two lightaxes are orthogonal to each other (the light axes are horizontal and 90degrees related), and 45 degrees to a vertical plane including theCamera Detector Axis. The Detector Axis for the Camera/22, which islocated in the negative “Z” plane, is approximately 45 degrees fromhorizontal (the camera bisects the horizontal light axes). With thisrelationship, the camera is looking at a dark field and is ideallyseeing only light coming from checks and blisters. The light sources andcamera are supported by structure 28 that can be vertically displacedand horizontally displaced to reposition the system for differentheight/diameter containers.

To start an inspection, the machine will transfer a container to theinspection station and following a time sufficient for the rotation ofthe container 10 to become stable, the Control 50 (FIGS. 4, 11 and 12)will begin the inspection. The Control will Rotate The Container AboutAxis Through Desired Angle 42 (FIG. 4). FIG. 5 illustrates theappearance of an anomaly 30 (a check or a blister) on the finish of thecontainer, as it would appear if captured by the camera as the bottlerotated through θ (theta) degree increments. As illustrated, thecontainer has an anomaly which is captured at ten of the elevenlocations spaced θ (theta) degrees. Such could occur by operating thecamera every time the bottle rotates θ (theta) degrees or could occur byholding the camera open for a prolonged period while strobing the lightsource each θ (theta) degrees. The anomalies are shown located within anangle of interest φ (phi) defining a partial elliptical path. TheControl 50 proceeds to Capture A Selected Number Of Images At θ (theta)Degree Increments 44 and the Control will then Locate The Upper EdgePoints Of Container 60. This edge 61 is shown in FIG. 5. The Controlwill then Fit Curve 62 to these edge points. This could be done usinglinear regression techniques. The fit curve 63 is shown in FIG. 6. TheControl then proceeds to Determine Vertical Peak Of Fitted Curve 64.This peak 65 is also shown in FIG. 6. The Control than proceeds toDefine Horizontal Line Through Peak 66 (line 67 in FIG. 6) and proceedsto Unwrap Image 68. This procedure is shown in FIG. 6 with verticaloffsets 69 which are defined by the number of pixels required to shiftthe fitted curve 63, at each vertical row, vertically to the peaktangent line 67. The Control will then Define The Center Of An AnomalyIn Each Captured Image 46.

FIG. 7 is a schematic presentation of the linear array of the ten imagesof an object captured through the 11 locations spaced θ (theta) degreesapart through the angle φ (phi) degrees with the center of the objectsplotted showing their “Y” location as a function of three horizontalbands and with their “X” location corresponding to its angularincrement. While the preferred embodiment unwraps the elliptical imageto define horizontal bands, the bands could be elliptically matched tothe pattern of the captured objects. FIGS. 8-10 are schematicpresentations of the objects sorted into each of the bands (1-2, 2-3,and 3-4) presented in FIG. 7. Each band represents a horizontal scanline or lines (a band could, for example be five horizontal scan lines).The width of each band (“B”) is shown as settable. Referring to FIG. 11,the Control 50 will Determine Objects In “N” Horizontal Bands “B” High70. The objects within a band define a “cluster”. The cluster objectsidentified in FIGS. 8 through 10 are:

Band 1 (1-2)—objects B, C, G, H, I;

Band 2 (2-3)—objects A, B, C, E, F, G, H, I, J, K;

Band 3 (3-4)—objects A, E, F, J, K;

The Control then proceeds to Define Band Having Most Objects As FirstCluster 72. In the above illustration, Band 2 has the most objects (9).If two bands have an identical number, the Control could pick either onefirst. The Control then proceeds to Remove Common Objects From OtherBands 74. The bands thus become:

Band 2 (2-3)—objects A, B, C, E, F, G, I, J, K;

When the Control asks the query Does Band With Next Highest Count OfObjects Have Objects Common To Other Bands? 76, the answer will be inthe negative—Band 2 has all the unique objects. No further revisions ofthe bands will take place. The objects in Band 2 will then be identifiedas a cluster.

Alternately, the bandwidth “B” could be set at 10 scan lines and all ofthe eleven objects could be located within the single band and treatedas a single cluster.

The Control next asks Does Any Cluster Have Gap(s) at least “X” ObjectsWide (X is settable) 78. In the event the query is answered in theaffirmative, the Control will Define Additional Clusters 79. If “X” wasset at three, this query for Band 2, would be answered in the negativesince there is a single gap one object wide. Had this gap been threeobjects wide (D,E,&F missing, for example) the Control would define theobjects to the left of the gap (A,B,&C) as one cluster and the objectsto the right of the gap (G-K) as a second cluster. It has been foundthat blisters generally have very small gaps and that a large gapindicates one or more checks. If the operator does not want to use thistool, “X” can be set at 12, for example.

The Control will then Define Maximum Separation Of Objects In EachCluster 80. Cluster 1 has ten spacings separating A from K. The Controlnow determines whether the cluster is a check or a blister. This is doneby answering the query “Max Separation of “N” Cluster≧ (greater than orequal to) “Z”?”82. Assuming Z is 8 (a settable input), when this inquiryis answered for Cluster 1 the answer will be yes and the Control willDefine “N” Cluster As Blister 86. Had the separation been less than 8,the Control would Define “N” Cluster As Check 84. This procedure will berepeated for each cluster.

If desired, a decision could be made at this point to pass all blistersand reject all checks but additional choices are provided by theControl. FIG. 12 illustrates the structure of the Control 50 fordiscriminating between a Blister or Check that will not result in abottle being rejected and one that will. The Control answers the query“Have All Clusters Been Defined As A Blister Or A Check? 90”. If theanswer is “yes”, the Control answers the query “Is Area Of Single ObjectIn A Blister Cluster≧ (greater than or equal to) AA?” Or Is Total AreaOf All Objects In A Blister Cluster≧ (greater than or equal to) BB? OrIs Number Of Objects In A Blister Cluster≧ (greater than or equal to)CC? or Is Total Area Of All Objects In All Blister Clusters≧ (greaterthan or equal to) DD? Or Is Total Number Of Objects In All BlisterClusters≧ (greater than or equal to) EE? 92. If this query is answeredin the affirmative, the Control will issue a Bottle Reject Signal 94.

The Control will also answer the query “Is Area Of Single Object InCheck Cluster≧ (greater than or equal to) FF?” Or Is Total Area Of AllObjects In A Check Cluster≧ (greater than or equal to) GG? Or Is NumberOf Objects In A Check Cluster≧ (greater than or equal to) HH? or IsTotal Area Of All Objects In All Check Clusters≧ (greater than or equalto) II? Or Is Total Number Of Objects In All Check Clusters≧ (greaterthan or equal to) JJ? 96. If this query is answered in the affirmative,the Control will also issue a Bottle Reject Signal 94.

1. A machine for inspecting the finish area of a glass containerrotating at an inspection station and discriminating between blistersand checks comprising a rotating device for rotating a bottle about itsaxis, a lighting device for illuminating the finish area of the rotatingbottle, a camera for imaging the finish area of the rotating bottle anda control for defining an array of objects captured by said camera at apredetermined number of angular increments of rotation, for defining aplurality of adjacent bands which include the captured objects, and foranalyzing the bands to identify a check or a blister.
 2. A machine forinspecting the finish area of a glass container rotating at aninspection station and discriminating between blisters and checksaccording to claim 1, wherein said control for analyzing the adjacentbands to identify a check or a blister comprises means for definingclusters of captured objects including means for determining the bandhaving the most captured objects, means for deleting the objects in theband having the most objects from the rest of the bands which includeobjects, and means for repeatedly determining the band of the rest ofthe bands having the most objects and deleting the objects in the bandof the rest of the bands having the most objects from the remainder ofthe bands until the objects in each band are unique, the unique objectsin each band defining a cluster.
 3. A machine for inspecting the finisharea of a glass container rotating at an inspection station anddiscriminating between blisters and checks according to claim 2, whereinsaid control for analyzing the adjacent bands to identify a check or ablister further comprises means for determining whether there is atleast one gap having a minimum size between objects in each cluster andmeans for defining additional clusters as a function of the number ofsuch gaps.
 4. A machine for inspecting the finish area of a glasscontainer rotating at an inspection station and discriminating betweenblisters and checks according to claim 2, wherein said control foranalyzing the adjacent bands to identify a check or a blister furthercomprises means for defining a selected separation of objects in acluster, means for determining the separation of the farthest separatedobjects in a cluster, and means for defining the cluster as a checkwhere separation of the farthest separated objects in the cluster isless than the selected separation.
 5. A machine for inspecting thefinish area of a glass container rotating at an inspection station anddiscriminating between blisters and checks according to claim 4, whereina cluster is defined as a check, said control further comprises meansfor determining the area of the largest object in the cluster and meansfor generating a reject signal in the event the largest object areaexceeds a predetermined area.
 6. A machine for inspecting the finisharea of a glass container rotating at an inspection station anddiscriminating between blisters and checks according to claim 4, whereina cluster is defined as a check, said control further comprises meansfor determining the total area of all objects in the cluster and meansfor generating a reject signal in the event the total area exceeds apredetermined area.
 7. A machine for inspecting the finish area of aglass container rotating at an inspection station and discriminatingbetween blisters and checks according to claim 4, wherein a cluster isdefined as a check, said control further comprises means for determiningthe number of objects in the cluster and means for generating a rejectsignal in the event that the number of objects in the cluster exceeds apredetermined number.
 8. A machine for inspecting the finish area of aglass container rotating at an inspection station and discriminatingbetween blisters and checks according to claim 4, wherein all checkclusters have been defined, said control further comprises means fordetermining the total area of all objects in all of the clusters whereinthe object has been defined as a check and means for generating a rejectsignal in the event the total area exceeds a predetermined area.
 9. Amachine for inspecting the finish area of a glass container rotating atan inspection station and discriminating between blisters and checksaccording to claim 4, wherein all of the check clusters have beenidentified, said control further comprises means for determining thetotal number of objects in all clusters defined as a check and means forgenerating a reject signal in the event that the total number of objectsin all of the clusters defined as a check exceeds a predeterminednumber.
 10. A machine for inspecting the finish area of a glasscontainer rotating at an inspection station and discriminating betweenblisters and checks according to claim 4, wherein said control furthercomprises means for defining a cluster as a blister where the furthestseparated objects in the cluster are separated by at least the selectedseparation.
 11. A machine for inspecting the finish area of a glasscontainer rotating at an inspection station and discriminating betweenblisters and checks according to claim 10, wherein a cluster is definedas a blister, said control further comprises means for determining thearea of the largest object in the cluster and means for generating areject signal in the event the largest object area exceeds apredetermined area.
 12. A machine for inspecting the finish area of aglass container rotating at an inspection station and discriminatingbetween blisters and checks according to claim 10, wherein a cluster isdefined as a blister, said control further comprises means fordetermining the total area of all objects in the cluster and means forgenerating a reject signal in the event the total area exceeds apredetermined area.
 13. A machine for inspecting the finish area of aglass container rotating at an inspection station and discriminatingbetween blisters and checks according to claim 10, wherein a cluster isdefined as a blister, said control further comprises means forgenerating a reject signal in the event that the number of objects inthe cluster exceeds a predetermined number.
 14. A machine for inspectingthe finish area of a glass container rotating at an inspection stationand discriminating between blisters and checks according to claim 10,wherein all blister clusters have been identified, said control furthercomprises means for determining the total area of all objects in all ofthe clusters wherein the object has been defined as a blister and meansfor generating a reject signal in the event the total area exceeds apredetermined area.
 15. A machine for inspecting the finish area of aglass container rotating at an inspection station and discriminatingbetween blisters and checks according to claim 10, wherein all blisterclusters have been identified, said control further comprises means fordetermining the total number of objects in all of the clustersidentified as a blister and means for generating a reject signal in theevent that the total number of objects in all of the clusters defined asa blister exceeds a predetermined number.
 16. A machine for inspectingthe finish area of a glass container rotating at an inspection stationand discriminating between blisters and checks according to claim 2,wherein said bands are horizontal bands.